CN118027512A

CN118027512A - Reinforcing member comprising structural adhesive on polyester carrier

Info

Publication number: CN118027512A
Application number: CN202410169388.1A
Authority: CN
Inventors: E·肖邦
Original assignee: Zephyros Inc
Current assignee: Zephyros Inc
Priority date: 2015-03-25
Filing date: 2016-03-24
Publication date: 2024-05-14
Also published as: EP3274397A1; CN107660224A; US20220041896A1; US11124678B2; US11787977B2; EP3274397B1; US20180057717A1; WO2016151093A1

Abstract

The present invention relates to a reinforcing member comprising a structural adhesive on a polyester carrier. The reinforcing member comprises a heat curable structural adhesive on a carrier member, wherein the carrier member comprises a fiber reinforced polyester material. The invention further relates to a method for producing such a reinforcing component and to the use thereof.

Description

Reinforcing member comprising structural adhesive on polyester carrier

The present application is a divisional application of application number 201680029501X, filed on the date of 2016, 3/24, entitled "reinforcing member comprising structural adhesive on polyester support".

Technical Field

The present invention relates to a reinforcing member comprising a heat curable structural adhesive on a carrier member, wherein the carrier member comprises a fiber reinforced polyester material. The invention further relates to a method for producing such a reinforcing component and to the use thereof.

Background

Structural adhesives are widely used to join components in the automotive industry, aircraft industry, and other industries.

Structural adhesives are typically provided on the carrier member as an outer layer or coating. The carrier member is typically prepared as an intermediate, followed by a layer of heat curable structural adhesive or an overcoat thereof, thereby providing a reinforcing member. The carrier members are preferably made of thermoplastic materials, especially because of their lighter weight compared to metals and alloys. Depending on the structure of the carrier member and the structure of the resulting unitary structure of the reinforcement member, it is generally desirable to prepare the carrier member by subjecting the thermoplastic material to processes such as compression molding, extrusion molding, injection molding, thermoforming, and the like, and then apply the heat-curable structural adhesive to the surface or portions of the surface of the frozen carrier member.

In conventional reinforcement members, the carrier member is typically made of thermoplastic polyamide. However, one of the disadvantages of these support members is that their E-modulus changes with changes in the atmosphere, in particular relative humidity. The E-modulus measured under standard conditions is satisfactory, for example, in the range of about 9GPa, depending on the supplier of the polyamide. However, it has in fact been revealed that a significantly lower E-modulus, e.g. in the range of only about 6GPa, should be used in Computer Aided Engineering (CAE) simulations, which are typically used for designing reinforcement members. It appears that polyamides are hygroscopic and sensitive to humidity. The level of water absorption depends on the polyamide type, the polyamide content, and the environmental conditions (temperature and relative humidity). Although the moisture uptake of polyamides is in principle a reversible phenomenon, drying begins only at temperatures above the glass transition temperature (65 ℃). Due to moisture absorption, the mechanical properties of the polyamide carrier change with changing environmental conditions, in particular humidity. This is particularly disadvantageous because modern automotive and aircraft industries operate globalization under construction equipment in many countries having different climates.

EP 1 854 704 discloses a joint formed for an article of manufacture such as a transportation vehicle (e.g., an automobile). The joint typically includes a connector bonded to the first and second members with a structural adhesive, which is a structural adhesive foam.

LANXESS high modulus thermoplastic, LXS-HPM-064EN, version 2014-10, is directed toAndIs a class 6 and 66 polyamide, and polybutylene terephthalate (PBT).

WO 2015/011686 relates to flexible films of thermoset adhesive materials that are non-tacky to the touch, are storage stable at room temperature, and can be cured at elevated temperatures with short cure times, and can be cured to produce tough flexible adhesive layers comprising adhesive to oily surfaces. The material is particularly useful in bonding dissimilar substrates together. The cured adhesive film may be used to bond a metal to a fiber reinforced resin, such as a glass fiber, carbon fiber, or aramid fiber reinforced epoxy or polyester based resin, by curing upon thermal activation.

There is a need for a reinforcing member that overcomes the shortcomings of the prior art.

It is an object of the present invention to provide a reinforcement member having advantages over the prior art. The reinforcing member should have excellent mechanical properties that remain substantially constant under varying climatic conditions, making the reinforcing member useful, for example, in the worldwide automotive and aircraft industries. Furthermore, they should have a light weight, should be available at low cost and should be easy to manufacture.

This object is achieved by the content of the claims of the present patent application.

Disclosure of Invention

In a first aspect, the invention relates to a reinforcing member comprising a heat curable structural adhesive on a carrier member, wherein the carrier member comprises a fiber reinforced polyester material. The reinforcing member includes a carrier member and a heat curable structural adhesive disposed on the carrier member. Typically, the heat curable structural adhesive is in intimate contact with the carrier member.

The heat curable structural adhesive of the reinforcing member is an activatable material configured to provide reinforcement upon application of heat, for example, by bonding to the inner wall of a hollow structure in which the reinforcing member has been placed. In addition to reinforcement, the reinforcement member may alternatively or additionally serve other purposes. In general, the reinforcement member may be used to reduce noise, vibration, and/or harshness (NVH). Preferably, the heat curable structural adhesive is configured to expand upon application of heat.

The carrier member according to the invention comprises a fibre reinforced polyester material. Typically, the carrier member may be shaped after heating, in particular by compression, extrusion, injection moulding or thermoforming techniques, enabling a complex three-dimensional structure of low weight to be obtained.

Surprisingly, it has been found that the fiber-reinforced polyester material according to the invention has great advantages over other materials conventionally used for the preparation of extrudable or injection-moldable carrier members, in particular polyamides, especially when the three-dimensional structure of the carrier member is complex. Fiber reinforced polyester materials provide an optimized compromise of various properties, in particular stiffness (e.g., in terms of E-modulus), weight (density), temperature resistance, and cost.

Further, it has surprisingly been found that carrier members based on fiber reinforced polyester materials are less moisture sensitive, such that their E-modulus does not need to be reduced for CAE simulation. Thus, the reinforcement member according to the invention can be used worldwide in various climatic conditions, and the simulation can be based on constant parameters such as E-modulus, temperature resistance (heat deflection temperature).

Furthermore, it has surprisingly been found that reinforcement members based on fiber-reinforced polyester carrier members are substantially smaller, especially in rather complex three-dimensional structures, and thus lighter than those based on polyamide carrier members providing similar reinforcement properties, at least at low humidity.

Detailed Description

All percentages are by weight (wt%) unless explicitly stated otherwise. The expressions like "comprising", "containing" and "including" are to be understood in an open sense, i.e. the presence of additional features associated with said expressions which are not mentioned are not excluded. However, in a preferred embodiment, these expressions may be replaced by the expression "consisting of … …" independently of each other, which is to be understood in a closed sense, i.e. the presence of additional features not mentioned in connection with the expression are excluded.

For the purposes of the present description, "heat-curable structural adhesive" refers to a material that is still heat-curable, i.e., to a structural adhesive prior to heating to a curing temperature (induction curing, crosslinking, hardening) or a temperature above the curing temperature (induction curing, crosslinking, hardening), while "structural adhesive material" refers to a structural adhesive after curing, crosslinking, and hardening, respectively. The heat-curable structural adhesive preferably dries to the touch at ambient temperature prior to heat curing and is capable of being processed at intermediate temperatures by techniques such as melt coating, extrusion or injection molding without significant crosslinking of the polymer system occurring.

The reinforcing member according to the present invention may be applied to various articles of manufacture. After heat curing, the structural adhesive material may bond a first face of one, two, or more components (e.g., members) to a second face of one, two, or more components. Such bonding may provide structural integrity and/or adhesion to components of the article, and may also provide sealing, damping (damping), or reinforcement, etc. to components of the article. Examples of such articles of manufacture include, but are not limited to, household or industrial appliances, furniture, storage containers, buildings, structures, or the like. In a preferred embodiment, the reinforcement member is applied to various components of the automobile, such as the body or frame member (e.g., frame rail (VEHICLE FRAME RAIL)). The heat curable structural adhesive on the carrier member may be applied to one or more surfaces of one of these components or articles in a pre-activated state, where it adheres to the surface while remaining heat curable, so that it will adhere to the surface as a melt without curing upon application. The heat curable structural adhesive may then be activated to cure or harden, optionally expanding and/or foaming. Upon application, the heat curable structural adhesive typically wets the surfaces, which contact adheres to these surfaces.

Preferably, the connection between the carrier member and the heat curable structural adhesive is an adhesive bond, a form fit, and/or a press fit (force-fit) (e.g., dovetail joint). In a preferred embodiment, the connection is seamless.

The size of the reinforcement member is not particularly limited and depends on the intended use of the reinforcement member, for example, the size and volume of the chamber in which it is to be placed. Typically in the range of a few centimeters, for example, about 1mm or about 10mm to a few centimeters, for example, about 300mm or about 500mm, or even a few meters.

Preferably, the reinforcement member has a 3D-shape, i.e. the reinforcement member has a cross section that does not include a constant thickness throughout its elongation. In preferred embodiments, at least a portion of the cross section of the reinforcement member is C-, E-, T-, U-, V-, I-, O-, and/or W-shaped. Additionally or alternatively, the reinforcement member may have a hollow structure, wherein the carrier member and the heat curable structural adhesive form a ring according to a preferred embodiment. The cross-section of the reinforcing member may vary with its length. The cross-section and/or the heat curable structural adhesive may vary with the length of the reinforcing member. The structure having a closed cross section may be made of two structures having an open cross section. For example, an O-shape may be formed by connecting two U-shapes to each other. In addition, the structures to be connected may be made by the same or by different techniques. For example, the shaped structure may be connected to an extruded structure.

The heat curable structural adhesive may be applied to one or more outer surfaces of the carrier member. Preferably, the heat curable structural adhesive covers at least a portion of the outer surface of the carrier member. In preferred embodiments, the heat curable structural adhesive covers at least about 5%, or at least about 10%, or at least about 30%, or at least about 50%, or at least 70%, or at least about 90%, or about the entire outer surface (100%) of the carrier member.

The relative weight ratio of the total weight of the carrier member to the total weight of the heat-curable structural adhesive is not particularly limited. In a preferred embodiment, the total weight of the carrier member is greater than the total weight of the heat curable structural adhesive, or the total weight of the carrier member is substantially the same as the total weight of the heat curable structural adhesive, or the total weight of the heat curable structural adhesive is greater than the total weight of the carrier member.

The carrier member provides support for the heat curable structural adhesive. While the primary purpose of the heat curable structural adhesive is to provide adhesion and reinforcement to the overall final structure, the primary purpose of the carrier is to provide reinforcement.

The size of the carrier member is not particularly limited.

Preferably, the carrier member has a 3D-shape, i.e. the carrier member has a cross section that does not comprise a constant thickness throughout its elongation. In preferred embodiments, at least a portion of the cross section of the support member is C-, E-, T-, U-, V-, I-, O-, and/or W-shaped.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has an E-modulus (tensile modulus, preferably determined under 1 mm-min ^-1 according to ISO 527-1, 2) of at least about 10GPa, or at least about 11GPa, or at least about 12GPa, more preferably at least about 13GPa, or at least about 14GPa, still more preferably at least about 15GPa, or at least about 16GPa, and even more preferably at least about 17GPa, or at least about 18GPa, or at least about 19GPa, or at least about 20GPa, or at least about 21 GPa. Preferably, the E-modulus is not humidity sensitive, i.e. the E-modulus of the carrier member preferably does not change by more than about 5%, more preferably by more than about 2% at different relative humidities (r.h.) of the ambient air, e.g. at 50% r.h. and at 70% r.h.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has a flexural modulus (preferably determined under 2mm min ^-1 according to ISO 178-a) of at least about 10GPa, or at least about 11GPa, or at least about 12GPa, more preferably at least about 13GPa, or at least about 14GPa, still more preferably at least about 15GPa, or at least about 16GPa, even more preferably at least about 17GPa, or at least about 17.5 GPa.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has a density (preferably determined according to ISO 1183) in the range of about 1770±350kg m ^-3, more preferably about 1770±300kg m ^-3, still more preferably about 1770±250kg m ^-3, still more preferably about 1770±200kg m ^-3, even more preferably about 1770±150kg m ^-3, most preferably about 1770±50kg m ^-3, in particular about 1770±25kg m ^-3.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has a deflection temperature (heat deflection temperature) under a load of 1.80MPa (preferably determined according to ISO 75-1, -2) of at least about 170 ℃, or at least about 175 ℃, or at least about 180 ℃, more preferably at least about 185 ℃, or at least about 190 ℃, still more preferably at least about 195 ℃, or at least about 200 ℃, and even more preferably at least about 205 ℃, or at least about 210 ℃.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has a deflection temperature (heat deflection temperature) under a load of 0.45MPa (preferably determined according to ISO 75-1, -2) of at least about 190 ℃, or at least about 195 ℃, or at least about 200 ℃, more preferably at least about 205 ℃, or at least about 210 ℃, still more preferably at least about 215 ℃, or at least about 220 ℃, and even more preferably at least about 225 ℃, or at least about 230 ℃.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has an E-modulus/density ratio in the range of about 10.5.+ -. 3.5MPa m ³ kg^-1, more preferably about 10.5.+ -. 3.0MPa m ³ kg^-1, still more preferably about 10.5.+ -. 2.5MPa m ³ kg^-1, still more preferably about 10.5.+ -. 2.0MPa m ³ kg^-1, even more preferably about 10.5.+ -. 1.5MPa m ³ kg^-1, most preferably about 10.5.+ -. 1.0MPa m ³ kg^-1, in particular about 10.5.+ -. 0.5MPa m ³kg^-1.

Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has an injection molding melting temperature (preferably determined according to ISO 294) in the range of about 280±30 ℃, more preferably about 280±20 ℃, most preferably about 280±10 ℃. Preferably, the material of the carrier member, in particular the fiber reinforced polyester material, has an injection molding mold temperature (preferably determined according to ISO 294) in the range of about 90±15 ℃, more preferably about 90±10 ℃, most preferably about 90±5 ℃.

Preferably, the material of the carrier member, in particular the fibre reinforced polyester material, has a melting temperature (preferably determined according to ISO 11357-1,3 under 10 ℃ mm ^-1) in the range of about 205 to 280 ℃, more preferably about 215 to 270 ℃, most preferably about 225 to 260 ℃.

The carrier member comprises, preferably consists essentially of, a fiber reinforced polyester material.

Preferably, at least about 90 wt%, more preferably at least about 95 wt% and most preferably at least about 99 wt% of the carrier member is comprised of a fiber-reinforced polyester material, relative to the total weight of the carrier member.

Preferably, the fiber reinforced polyester material comprises fibers, one or more polyesters, and optionally one or more additives conventionally used in polymer compositions, such as fillers, dyes, plasticizers, stabilizers, antioxidants, and the like.

Preferably, the sum of the total weight of the fibers and the total weight of the one or more polyesters comprises at least about 80 wt%, more preferably at least about 85 wt%, still more preferably at least about 90 wt%, and most preferably at least about 95 wt% of the total weight of the carrier member.

The carrier member comprises a fibre-reinforced material, i.e. a material in which the fibres are dispersed in such a way that they provide reinforcement.

The fibers of the fiber-reinforced polyester material are not particularly limited. The fibers may be natural or synthetic, or mixtures thereof. Typically, the fibers are elongated fibers, e.g., substantially uniaxial particles (uniaxed particles).

Natural fibers include, but are not limited to, fibers derived from plants (e.g., cellulose-based fibers such as cotton, linen (linen), jute, flax (flax), ramie (ramie), sisal (sisal), hemp, and wood) and fibers derived from minerals (e.g., asbestos).

Synthetic fibers include, but are not limited to, glass fibers, carbon fibers, and aramid fibers. Preferably, the fiber reinforced polyester material comprises glass fibers or carbon fibers. In a preferred embodiment, the carbon fibers are continuous filament carbon fibers, which are obtainable, for example, by pyrolysis or decomposition of carbon-containing fibers such as rayon, polyacrylonitrile, and petroleum pitch by heating. Glass fibers are particularly preferred.

The fibers may be combined into bundles with a polymeric binder, such as a polyamide terpolymer binder.

The average length of the fibers is preferably in the range of a few μm, for example, about 20.+ -. 10. Mu.m, or about 40.+ -. 20. Mu.m, or about 60.+ -. 30. Mu.m, or about 80.+ -. 40. Mu.m, or about 100.+ -. 50. Mu.m, or about 150.+ -. 75. Mu.m, or about 200.+ -. 100. Mu.m, or about 500.+ -. 250. Mu.m.

Preferably, the content of fibers, preferably glass fibers or carbon fibers, is in the range of about 15 wt.% to about 70 wt.%, relative to the total weight of the fiber reinforced polyester material.

In a preferred embodiment, the content of fibers, preferably glass fibers or carbon fibers, is in the range of about 45±25 wt%, more preferably about 45±20 wt%, still more preferably about 45±15 wt%, even more preferably about 45±10 wt%, most preferably about 45±5 wt%, relative to the total weight of the fiber reinforced polyester material. In other preferred embodiments, the content of fibers, preferably glass fibers or carbon fibers, is in the range of about 55±25 wt%, more preferably about 55±20 wt%, still more preferably about 55±15 wt%, even more preferably about 55±10 wt%, most preferably about 55±5 wt%, relative to the total weight of the fiber reinforced polyester material. In yet another preferred embodiment, the content of fibers, preferably glass fibers or carbon fibers is in the range of about 65±25 wt%, more preferably about 65±20 wt%, still more preferably about 65±15 wt%, even more preferably about 65±10 wt%, most preferably about 65±5 wt%, relative to the total weight of the fiber reinforced polyester material.

The carrier member comprises a polyester material. The polyester material may comprise one or more different polyesters. When the polyester materials comprise different polyesters, they may differ in chemical composition and/or average molecular weight.

Independently of each other, the one or more polyesters may be linear or branched, aromatic or aliphatic, homo-or copolymers (e.g., co-or terpolymers) derived from dicarboxylic acids and diols and/or from hydroxycarboxylic acids.

The average molecular weight of one or more polyesters in the polyester material is not particularly limited. The weight average molecular weight is preferably in the range of about 10,000 to about 250,000g/mol, more preferably about 25,000 to about 100,000 g/mol. The dispersity Mw/Mn is preferably in the range of about 1.2 to about 4, more preferably about 1.8 to about 2.8.

Preferably, the polyester material comprises an aromatic polyester, preferably derived from one or more aromatic dicarboxylic acids and/or one or more aliphatic diols. The aromatic polyesters may be derived from several different monomers.

The one or more aromatic dicarboxylic acids are preferably selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, and mixtures thereof. Terephthalic acid is particularly preferred. The one or more aliphatic diols are preferably selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, and mixtures thereof.

Preferably, the polyester material comprises an aromatic polyester comprising, preferably consisting essentially of, repeating units of the general formula (I):

-O-(CH₂)_n-O-C(＝O)-C₆H₄-C(＝O)-(I)，

wherein n is 2, 3, 4, 5 or 6, preferably 2 or 4.

Preferred representatives are polyethylene terephthalate (PET), modified PET, polybutylene terephthalate (PBT) and modified PBT.

Preferably, the fiber reinforced polyester material comprises a blend comprising a first polyester, preferably a first aromatic polyester, and a second polyester, preferably a second aromatic polyester, which preferably comprises, independently of each other, repeating units of the general formula (I), preferably essentially consisting of repeating units of the general formula (I).

In a particularly preferred embodiment, the first polyester is polybutylene terephthalate (PBT) and the second polyester is polyethylene terephthalate (PET).

Independently of each other, PBT and PET can be modified. For example, cyclohexanedimethanol may be added to the polymer backbone to replace a portion of butanediol and a portion of ethylene glycol, respectively. Likewise, phthalic acid, isophthalic acid and/or dimethylterephthalic acid may be added to the polymer backbone in place of a portion of the terephthalic acid.

Since the polyester material should have the most desirable mechanical strength, it preferably has a high degree of crystallinity, typically at least 60%.

The relative weight ratio of the first polyester to the second polyester is not particularly limited. In a preferred embodiment, the first polyester is present in excess. In other preferred embodiments, the second polyester is present in excess. In yet another preferred embodiment, the first polyester is present in an amount substantially the same as the second polyester.

Preferably, the relative weight ratio of the first polyester to the second polyester is in the range of from about 1:10 to about 10:1, more preferably from about 1:5 to about 5:1, still more preferably from about 1:4 to about 4:1, still more preferably from about 1:3 to about 3:1, even more preferably from about 1:2.5 to about 2.5:1, most preferably from about 1:2 to about 2:1, especially from about 1:1.5 to about 1.5:1.

Preferably, the fiber reinforced polyester material comprises recycled polyester. When it is also possible that the fibers are at least partially recycled fibers, in a preferred embodiment the polyester material comprises at least partially recycled polyester.

Recycled polyesters include chemically recycled polyesters and mechanically recycled polyesters. In chemical regeneration, the polymer backbone is broken and the constituent elements (building blocks) of the polyester, i.e., carboxylic acid and alcohol or intermediates, are separated to synthesize the nascent polymer. In mechanical regeneration, the original polymer properties are maintained or reconstructed (reconstitute).

The content of the recycled polyester is not particularly limited with respect to the content of the non-recycled (i.e., virgin) polyester. In preferred embodiments, the recycled polyester is present in an amount of at least about 10 wt%, or at least about 20 wt%, or at least about 30 wt%, or at least about 40 wt%, or at least about 50 wt%, or at least about 60 wt%, or at least about 70 wt%, or at least about 80 wt%, or at least about 90 wt%, or substantially about 100 wt%, relative to the total weight of polyester contained in the polyester material.

When the polyester material comprises a blend of a first polyester and a second polyester, preferably the first polyester and/or the second polyester comprises recycled polyester.

Because the global consumption of PET is significantly higher than that of PBT, recycled PET is generally more readily available than recycled PBT. Thus, when the polyester material according to the invention comprises a blend of PBT and PET, the PET component preferably comprises recycled PET, while the PBT component also comprises recycled PBT or does not comprise recycled PBT.

In addition to the carrier member, the reinforcement member according to the invention comprises a heat curable structural adhesive.

The heat curable structural adhesive according to the present invention is preferably already and will be processed at different levels at different temperatures until it is finally used for its intended purpose of bonding components. The heat curable structural adhesive is included with the carrier member in the reinforcing member and thus is typically formed during the manufacturing process of the reinforcing member. The heat curable structural adhesive is typically applied to the carrier member at an intermediate elevated temperature at which the heat curable structural adhesive can be formed without curing and without exhibiting adhesive properties. After cooling to ambient temperature, the heat curable structural adhesive on the carrier member is preferably solid and dry to the touch. The heat curable structural adhesive is preferably solid at ambient temperature and dry to the touch, can be activated at an elevated activation temperature to exhibit adhesive properties, and can in principle be reformed without curing at a temperature above ambient temperature and below the elevated activation temperature.

Preferably, the heat curable structural adhesive is applied to one or more outer surfaces or portions of the surface of the carrier member. Preferably, the heat curable structural adhesive may be considered as a coating of the carrier member.

The layer thickness of the heat curable structural adhesive on the carrier member is not particularly limited and depends on the intended use of the reinforcing member, e.g., the size and volume of the chamber in which it is to be placed. In preferred embodiments, the thickness is at least about 0.1mm, or at least about 0.5mm, or at least about 1mm, or at least about 3mm.

The shape of the heat-curable structural adhesive on the carrier member is not particularly limited. In a preferred embodiment, the heat curable structural adhesive forms a uniform coating of the carrier member such that the exterior shape of the reinforcing member does not substantially change with the heat curable structural adhesive, but is substantially based on the shape of the carrier material. In other preferred embodiments, the heat curable structural adhesive forms a non-uniform coating of the carrier member such that the exterior shape of the reinforcing member is different from the exterior shape of the carrier material.

Preferably, the heat-curable structural adhesive is solid at room temperature and dry to the touch and can be processed by heating at a temperature below the temperature at which it will cure (curing temperature), in particular so that the heat-curable structural adhesive can be processed, for example, by melt coating, extrusion or injection molding and can resolidify upon cooling without reacting during the forming process. When the heat curable structural adhesive contains a blowing agent, the material preferably does not yet expand under these conditions, i.e. at a temperature below the curing temperature.

The heat curable structural adhesive preferably dries to the touch at ambient temperature (20 ℃) and preferably can be pelletized and shaped at a temperature below the activation temperature of the curing agent and any foaming agent that may be present. The heat curable structural adhesive thus preferably has a melting point in the range of about 80 ℃ to about 120 ℃, more preferably about 80 ℃ to about 110 ℃; preferably having a cure temperature preferably in the range of about 130 ℃ to about 210 ℃, more preferably about 130 ℃ to about 150 ℃.

The present invention is particularly directed to providing a heat curable structural adhesive of structural adhesive material when cured which can be used in the automotive and aerospace industries and which adds strength to the area where the adhesive is used by fixing the bond between substrates (components) and adding rigidity to the bond without imparting undesirable brittleness.

The heat-curable structural adhesive according to the present invention is not particularly limited and includes any conventional heat-curable structural adhesive commercially available.

Preferably, the heat curable structural adhesive according to the present invention is epoxy-based, i.e. comprises an epoxy material, preferably in combination with a curing agent. In addition to the epoxy material and the curing agent, the heat curable structural adhesive preferably contains one or more additional components such as a curing accelerator, an impact modifier, a flexibilizer, a foaming agent, a foaming accelerator, a thermoplastic modifier, and the like.

In a preferred embodiment, the heat curable structural adhesive comprises an epoxy resin, as well as a curing agent, and an additional-curing accelerator; and/or

-An impact modifier selected from the group consisting of epoxy-functionalized impact modifiers and core/shell impact modifiers; and/or

-A flexibilizer selected from the group consisting of hydroxyl-terminated urethane prepolymers and polyvinyl butyral resins; and/or

-A foaming agent, optionally in combination with a foaming promoter; and/or

-A thermoplastic modifier selected from phenoxy resins.

In a particularly preferred embodiment, the heat curable structural adhesive comprises an epoxy resin and a curing agent, and additional

-A curing accelerator; and/or

-A combination of a first impact modifier selected from epoxy-functionalized impact modifiers and a second impact modifier selected from core/shell impact modifiers; and/or

-A combination of a first flexibilizer selected from hydroxyl-terminated urethane prepolymers and a second flexibilizer selected from polyvinyl butyral resins; and/or

-A combination of a foaming agent and a foaming promoter.

In other particularly preferred embodiments, the heat curable structural adhesive comprises an epoxy resin and a curing agent, and additional

-A curing accelerator; and/or

-An impact modifier selected from epoxy-functionalized impact modifiers; and/or-a combination of a first pliable agent selected from a hydroxyl terminated urethane prepolymer and a second pliable agent selected from a polyvinyl butyral resin; and/or

-A thermoplastic modifier selected from phenoxy resins.

In a preferred embodiment, the heat-curable structural adhesive is foamable in the case that it contains a physical and/or chemical foaming agent, optionally in combination with a foaming promoter. In this embodiment, the structural adhesive will expand to a volume greater than its volume in the unexpanded state (e.g., at least about 5% greater, at least about 20% greater, or possibly even at least about 50% greater). Where the structural adhesive is to be used in areas where it is desired to reduce input distortion, it is preferred that the volumetric expansion be relatively low such that the expanded volume is no greater than about 400%, more preferably no greater than about 300%, even more preferably no greater than about 200% relative to the original unexpanded volume.

The heat curable structural adhesive preferably comprises an epoxy resin or a mixture of various epoxy resins.

For purposes of this specification, "epoxy resin" refers to any conventional dimeric, oligomeric or polymeric epoxy material containing at least one epoxy functional group, i.e., one or more reactive oxirane rings that are polymerizable by a ring-opening reaction. Furthermore, the term "epoxy resin" refers to an epoxy resin or any combination of epoxy resins. The epoxy resin may increase the adhesive properties, the flow properties, or both, of the heat curable structural adhesive. The hardening of the heat curable structural adhesive depends at least in part on the presence of reactive oxirane rings in the epoxy resin; upon heating, the reactive oxirane ring reacts with, for example, a curing agent, thereby effecting cross-linking (curing) and hardening of the thermally curable structural adhesive, thereby providing a structural adhesive material.

Preferably, the heat curable structural adhesive comprises about 2 wt% to about 70 wt%, more preferably about 15 wt% to about 55 wt%, most preferably about 25 wt% to about 45 wt% epoxy resin relative to the total weight of the heat curable structural adhesive.

The epoxy resin may be difunctional, trifunctional, multifunctional, or a combination thereof. The epoxy resin may be aliphatic, cycloaliphatic, aromatic, or any combination thereof. The epoxy resin may be supplied as a solid (e.g., as particles (pellet), blocks (chunk), or flakes (piece), etc.), or as a liquid, or both. As used herein, an epoxy resin is considered a solid epoxy resin if it is solid at a temperature of 23 ℃ and a liquid epoxy resin if it is liquid at 23 ℃.

Preferably, the epoxy resin includes an epoxy resin selected from aromatic epoxy resins and aliphatic epoxy resins, with aromatic epoxy resins being preferred. Preferably, the epoxy resin is selected from the group consisting of bisphenol-a epoxy resins (e.g., diglycidyl ether of bisphenol-a), bisphenol-F epoxy resins (e.g., diglycidyl ether of bisphenol-F), novolac epoxy resins (e.g., epoxy Phenol Novolac (EPN) and epoxy resol (ECN)), aliphatic epoxy resins (e.g., glycidyl epoxy resins and cycloaliphatic epoxides), and glycidylamine type epoxy resins (e.g., triglycidyl para-aminophenol and N, N-tetraglycidyl-4, 4-methylenedibenzylamine). Various mixtures of different epoxy resins may be employed in accordance with the present invention. Suitable epoxy resins are commercially available, for example Dow Chemical Company under the trade nameProducts under (e.g., DER 331, DER 661, DER 662); product of Hexion SPECIALTY CHEMICALS under the trade names EPON (e.g., EPON 828, EPON 863); huntsman Chemical under the trade name/>(E.g., GY 281, GY 282, GY 285, GT 6097, and GT 7071).

The heat curable structural adhesive preferably comprises a curing agent or a mixture of various curing agents.

The curing agent aids in the curing of the heat curable structural adhesive by crosslinking the epoxy resin with the other components of the heat curable structural adhesive. The curing agent may be difunctional, trifunctional or multifunctional.

Preferably, the heat curable structural adhesive comprises from about 0.001 wt% to about 9 wt%, more preferably from about 0.1 wt% to about 6 wt%, and most preferably from about 2 wt% to about 6 wt% of one or more curing agents, relative to the total weight of the heat curable structural adhesive.

The curing agent is preferably aliphatic or aromatic. Preferably, the curing agent is selected from aliphatic or aromatic amines or their respective adducts, amidoamines, polyamides, cycloaliphatic amines, anhydrides, polycarboxylic polyesters, isocyanates, phenolic resins (e.g., phenol or cresol novolac resins, copolymers such as those of phenol terpenes, polyvinylphenols, or bisphenol-a formaldehyde copolymers, or dihydroxyphenyl alkanes, etc.), dihydrazides, sulfonamides, diaminodiphenyl sulfones, anhydrides, thiols, imidazoles, ureas, tertiary amines, BF ₃ complexes, or mixtures thereof. Particularly preferred curing agents include, but are not limited to, modified and unmodified polyamines or polyamides such as triethylenetetramine, diethylenetriamine, tetraethylenepentamine, cyanoguanidine, dicyandiamide and the like. Suitable curing agents are commercially available, e.g., alzchem under the trade nameThe following Products (e.g., dyhard 1005) or Amicure from Air Products.

The curing agent may be activated by mixing with other components of the heat curable structural adhesive or by exposure to conditions such as radiation, humidity, or pressure. Preferably, the thermosettability of the thermosettable structural adhesive is dependent on the thermal activation of the curing agent such that it is preferably potentially thermally activated.

The heat-curable structural adhesive may additionally include an accelerator for a curing agent (curing accelerator). Suitable curing accelerators include, but are not limited to, modified or unmodified ureas such as methylenebis (phenyldimethylurea), imidazoles, hindered amines (blocked amines), or combinations thereof. Suitable curing accelerators are commercially available, for example, under the trade nameLower products (e.g., omicure U).

Preferably, the heat curable structural adhesive comprises from about 0.001 wt% to about 9wt%, more preferably from about 0.1wt% to about 6 wt%, and most preferably from about 2 wt% to about 6 wt% of one or more cure accelerators, relative to the total weight of the heat curable structural adhesive.

In a preferred embodiment, the heat curable structural adhesive includes at least one cure accelerator. In other preferred embodiments, the heat curable structural adhesive does not include a cure accelerator.

In addition to the epoxy resin and curing agent, the heat curable structural adhesive may contain other additives such as impact modifiers, flexibilizers and other elongation promoting additives, fillers, and other polymers or copolymers, blowing agents, foaming promoters and other additives.

Preferably, the heat curable structural adhesive includes an impact modifier or a mixture of various impact modifiers, sometimes also referred to as a "toughening agent (toughening agent)". Preferably, the impact modifier contributes to the desired mechanical properties of the adhesive, such as T-peel strength, by means of the distribution of energy within the adhesive system.

For purposes of this specification, the term "impact modifier" may include, but is not limited to, an impact modifier or impact modifiers. Preferred impact modifiers include, but are not limited to, thermoplastics, thermosets or thermosettable materials (thermosettables), elastomers or combinations thereof, and the like. In a preferred embodiment, the impact modifier comprises an elastomer (including an elastomer-containing material), a core/shell polymer (which may include, but is not limited to, an elastomer), or a combination thereof.

Preferably, the heat curable structural adhesive comprises at least about 4 wt%, more preferably at least about 10 wt%, and most preferably at least about 20 wt% of impact modifier relative to the total weight of the heat curable structural adhesive; preferably no greater than about 70 wt%, more preferably no greater than about 40 wt%, and most preferably no greater than about 30 wt% of impact modifier.

In a preferred embodiment, the heat curable structural adhesive comprises at least two impact modifiers comprising a substantial portion of a core/shell polymer (core/shell impact modifier).

For purposes of this specification, the term "core/shell impact modifier" refers to an impact modifier in which a substantial portion thereof (e.g., greater than 30 wt.%, 50 wt.%, 70 wt.% or more) is composed of a first polymeric material (i.e., a first material or core material) substantially completely encapsulated by a second polymeric material (i.e., a second material or shell material). As used herein, the first and second polymeric materials may be composed of one, two, three or more polymers combined and/or reacted together (e.g., sequential polymerization), or may be separate parts or the same core/shell system.

The first and second polymeric materials of the core/shell impact modifier may include, but are not limited to, elastomers, polymers, thermoplastics, copolymers, other components, combinations thereof, or the like, independently of each other. In preferred embodiments, the first polymeric material, the second polymeric material, or both of the core/shell impact modifier include, but are not limited to, or consist essentially entirely (e.g., at least 70 wt.%, 80 wt.%, 90 wt.% or more) of one or more thermoplastics. Exemplary thermoplastics include, but are not limited to, polystyrene, polyacrylonitrile, polyacrylate, polyacetate, polyamide, and polyolefin.

Preferred core/shell impact modifiers are formed by emulsion polymerization followed by coagulation or spray drying. In certain applications, the agglomeration level of the core/shell impact modifier has been found to be particularly desirable for promoting adhesion to surfaces having impurities thereon, such as dust, or oil (e.g., metal stamping oil). Such impact modifiers may reduce the likelihood of poor adhesion (as opposed to poor cohesion).

Examples of useful core/shell graft polymers that can be used as core/shell impact modifiers are those containing a hard graft of a compound such as styrene, acrylonitrile, or methyl methacrylate to a core made of a polymer containing a soft or elastomeric compound such as butadiene or butyl acrylate.

Preferred core/shell impact modifiers include core polymers obtainable by polymerizing a first monomer mixture comprising butyl acrylate, but may also comprise ethyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate or other alkyl acrylates or mixtures thereof. The first monomer mixture may also include other copolymerizable materials containing compounds such as styrene, vinyl acetate, methyl methacrylate, butadiene, or isoprene. The first monomer mixture may also include a cross-linking agent having more than two non-conjugated double bonds of approximately equal reactivity, such as ethylene glycol diacrylate, butylene glycol dimethacrylate, and the like.

In addition, the first monomer mixture may also include a graft-linking monomer having more than two non-conjugated double bonds of unequal reactivity, such as diallyl maleate and allyl methacrylate. The shell polymers of these core/shell impact modifiers are preferably obtainable by polymerizing a second monomer mixture comprising methyl methacrylate and optionally other alkyl methacrylates such as ethyl methacrylate and butyl methacrylate or mixtures thereof and the like. Preferably, the second monomer composition comprises up to 40% by weight or more of monomers selected from styrene, vinyl acetate, vinyl chloride, and the like, relative to the total weight of all monomers in the second monomer composition. Core/shell impact modifiers of this type are known, for example, from U.S. Pat. No. 3,985,703. Additional graft copolymers which can be used as core/shell impact modifiers according to the invention are described in US 3,984,497; U.S. Pat. No. 3,944,631; US 4,034,013; US 4,096,202; US 4,304,709; US 4,306,040; US 4,495,324; and US 4,536,436.

Further preferred core/shell graft polymers which may be used as core/shell impact modifiers according to the invention include methacrylate-butadiene-styrene copolymers (MBS), which may be obtained by polymerizing methyl methacrylate in the presence of polybutadiene or polybutadiene copolymer rubber. The MBS graft polymer typically comprises a styrene butadiene rubber core and a shell of an acrylic polymer or copolymer.

Examples of other preferred core/shell graft polymers that may be used as core/shell impact modifiers according to the present invention include, but are not limited to, acrylonitrile-butadiene-styrene copolymer (ABS), methacrylate-acrylonitrile-butadiene-styrene copolymer (MABS), acrylate-styrene-acrylonitrile copolymer (ASA), all acrylics, styrene-acrylonitrile (SAEPDM) grafted onto the elastomeric backbone of the ethylene-acrylonitrile diene monomer, and methacrylic-acrylic rubber styrene copolymer (MAS), and the like, as well as mixtures thereof. Other preferred core/shell impact modifiers include a shell of polymethyl methacrylate (PMMA) or acrylonitrile polymer or copolymer and a core of butadiene or styrene-butadiene polymer material.

Useful core/shell impact modifiers are commercially available, for example, from Dow Chemical under the trade nameLower products (e.g., EXL-2691A and EXL-2650A). Other preferred materials are Arkema CLEARSTRENGTH E-950 and Biostrength 150. Other preferred core/shell impact modifiers include, but are not limited to, those having a relatively soft acrylate core (e.g., polybutyl acrylate or other low Tg acrylate) and a hard acrylate shell (e.g., PMMA). Preferred materials are Arkema under the trade name DURASTRENGTH D-440 and Dow Chemical sold under the trade names Paraloid EXL-2300 and 2314.

In a preferred embodiment, the heat curable structural adhesive comprises at least one core/shell impact modifier. In other preferred embodiments, the heat curable structural adhesive does not include a core/shell impact modifier.

In other preferred embodiments, the impact modifier comprises an elastomer or rubber. Preferred examples include, but are not limited to, particulate (e.g., ground or crushed) elastomers or rubbers or adducts thereof (e.g., carboxyl-terminated butadiene acrylonitrile rubber/epoxy adducts, epoxy/CTBN adducts). CTBN liquid polymers undergo an addition esterification reaction with an epoxy resin, allowing them to be used as elastomer modifiers, thereby improving impact strength, peel strength and crack resistance. Examples of such impact modifiers include, but are not limited to, HYPOX RK 8-4 of CVC SPECIALTY CHEMICALS, or ARALDITE LT 1522ES of Huntsman Chemical.

Preferred epoxy/CTBN (carboxyl terminated butadiene acrylonitrile polymer) adducts, which may be included as impact modifiers, in the heat curable structural adhesives include, but are not limited to, epoxy functional polymers that may be saturated or unsaturated, cyclic or acyclic, aliphatic, cycloaliphatic, aromatic or heterocyclic. The epoxy functional polymer may have pendant or terminal hydroxyl groups if desired. They may contain substituents such as halogen, hydroxyl and ether groups. Useful classes of these materials include polyepoxides containing an epoxy polyether obtained by reacting an epihalohydrin (such as epichlorohydrin or epibromohydrin) with a di-or polyol in the presence of a base. Suitable polyols include, but are not limited to, polyphenols such as resorcinol; catechol; hydroquinone; bis (4-hydroxyphenyl) -2, 2-propane, bisphenol-a; bis (4-hydroxyphenyl) -1, 1-isobutane; 4, 4-dihydroxybenzophenone; bis (4-hydroxyphenol) -1, 1-ethane; bis (2-hydroxyphenyl) -methane and 1, 5-hydroxynaphthalene.

Liquid rubber modified epoxy resins (adducts) may also be preferred. Particularly preferred are solid epoxy adducts of carboxylated, solid, high molecular weight nitrile rubbers. It may also be desirable to include other nitrile rubbers, such as hydrogenated nitrile rubber, as part of the overall impact modifier. These may work synergistically with the core/shell impact modifiers to increase elongation, but should be used in small amounts to maintain a desired Tg, for example above 80 ℃.

Preferably, the heat curable structural adhesive comprises an impact modifier, or a mixture of various flexibilizers and various elongation promoting additives.

The presence of specific polymers that are not epoxy reactive in the heat curable structural adhesive may result in increased elongation at break and/or flexibility of the cured structural adhesive material. For purposes of illustration, such polymers are referred to as "flexibilizers". The term also includes elongation promoting additives. For purposes of this specification, the term "pliable agent" refers to a single pliable agent or a combination of a plurality of different pliable agents.

Without being bound by theory, it is believed that the polymer mixture undergoes phase separation during curing of the epoxy-reactive component, providing softer regions within the cured structural adhesive material. Alternatively, the pliable agent may act as a plasticizer compatible with the epoxy resin, but forms domains between the crosslinked epoxy molecules that promote the ability of the material to deform without breaking. The flexibilizer can be used to enhance the plasticity of the overall polymer matrix by, for example, phase separation of the rubber modified epoxy and the use of core/shell impact modifiers, which in turn makes the addition of other types of toughening agents more efficient.

Preferably, the heat curable structural adhesive comprises at least about 2 wt%, more preferably at least about 3 wt%, and most preferably at least about 5 wt% of the pliable agent, relative to the total weight of the heat curable structural adhesive; preferably no greater than about 50 weight percent, more preferably no greater than about 35 weight percent, and most preferably no greater than about 20 weight percent of the pliable agent, although slightly higher and lower percentages may be possible unless otherwise indicated. It is also contemplated that the amount of the flexibilizer may be higher in embodiments where the flexibilizer is modified with an epoxy component.

Preferred flexibilizing agents that may be included in the heat curable structural adhesive are hydroxyl terminated urethane polymers or prepolymers. Isocyanate ends should be avoided as this would result in a simple component material that limits storage stability due to the reaction of isocyanate functionality with moisture in the atmosphere or within the material. Hydroxyl-terminated urethane prepolymers are commercially available, for example, lubrizol under the trade nameThe following products and Merquinson under the trade nameThe following products.

Alternative or additional flexibilizers that may be included in the heat curable structural adhesive are polyvinyl esters, preferably polyvinyl butyral resins such as Butvar resins available from Solutia, especially Butvar90, and Mowital resins available from Kuraray are useful.

Other preferred flexibilizers are modified, including but not limited to amine modified, epoxy modified, or simultaneously modified polymers. These polymers may include, but are not limited to, thermoplastics, thermosets or thermosettable materials, elastomers, combinations thereof, or the like. These polymers may be modified with aromatic or non-aromatic epoxies, and/or may be modified with bisphenol-F, bisphenol-a, combinations thereof, or other epoxy types.

Preferred modifying flexibilizers are epoxidized polysulfides, for example, akzo Nobel under the trade names Thioplast EPS-350 and EPS-80; or Huntsman Chemical available under the trade name Flexibilizer DY 965 CH.

Further preferred modifying flexibilizers are epoxy dimer acid elastomers, such as those available under the trade name HYPOX DA323 for CVC SPECIALTY CHEMICALS.

Still further preferred modified flexibilizers are polyurethane modified epoxies, such as those available from GNS Technologies under the trade names GME-3210 and G E-3220. Without being bound by theory, it is believed that when the heat curable structural adhesive includes a polyurethane modified epoxy pliable agent, the heat curable structural adhesive can substantially maintain impact strength (e.g., impact resistance) at low temperatures while minimizing the decrease in Tg (e.g., as compared to other pliable agents).

Still further preferred modified flexibilizers are amine or epoxy terminated polyethers, e.g., huntsman Chemical under the trade name(E.g., D-2000) and Dow Chemical Company under the trade name/>(E.g., 732) available under the recipe.

Further preferred flexibilizers are based on cashew nutshell liquid, e.g. under the trade nameAn epoxidation liquid available under (e.g., NC-514 and Lite 2513 HP).

Thermoplastic polyamides with low melting points are also particularly useful, for example, duPont under the trade nameThose available below. Preferably, the polyamide resin is melted at a temperature in the range of about 110 ℃ to about 175 ℃, more preferably about 115 ℃ to about 160 ℃.

All of the various pliable agents discussed herein may be included in the heat curable structural adhesive alone or in combination with one another, unless otherwise indicated.

In a preferred embodiment, the heat curable structural adhesive comprises at least one pliable agent. In other preferred embodiments, the heat curable structural adhesive does not include a pliable agent.

Preferably, the heat curable structural adhesive includes one or more fillers including, but not limited to, particulate materials (e.g., powders), beads, or microspheres, and the like.

Fillers can impart properties such as strength, dimensional stability, and impact resistance to the cured structural adhesive material. However, fillers can reduce elongation. Fillers can also reduce formulation costs and provide compositions that have less tackiness prior to curing.

Preferably, the heat curable structural adhesive comprises from about 2% to about 30% by weight or more, more preferably from about 8% to about 25% by weight of filler relative to the total weight of the heat curable structural adhesive. However, it is preferred that the overall filler content be less than 20% by weight in order to maintain the desired elongation of the cured structural adhesive material.

Preferably, when the filler is a clay or similar clay-like material, the heat-curable structural adhesive comprises from about 0% to about 2% by weight, more preferably no more than about 1% by weight, of clay or similar filler, relative to the total weight of the heat-curable structural adhesive.

Preferably, when the filler is a powdered material having an average particle size of about 0.01 μm to about 50 μm, preferably about 1 μm to about 25 μm, for example, a mineral filler, the heat-curable structural adhesive preferably comprises about 5% to about 40% by weight, more preferably about 10% to about 25% by weight, of the powdered material relative to the total weight of the heat-curable structural adhesive.

Preferred fillers include, but are not limited to, silica, diatomaceous earth, glass, clays (e.g., including nanoclays), talc, pigments, colorants, glass beads or bubbles, carbon or ceramic fibers, chopped or continuous glass, ceramic, aramid (e.g., kevlar) or carbon fibers, and nylon or polyamide fibers. Examples of suitable fillers include, but are not limited to, wollastonite, talc, vermiculite, pyrophyllite, sauconite, saponite, nontronite, montmorillonite or mixtures thereof. Suitable clays may or may not be calcined, including, but not limited to, clays in the group consisting of kaolinite, illite, chlorite (chloritem), smectite (smecitite) or sepiolite. The clay may also contain minor amounts of other ingredients such as carbonates, feldspar, mica and quartz. The fibers may improve the reinforcement of the cured structural adhesive material.

In a preferred embodiment, the heat curable structural adhesive comprises one or more mineral or stone fillers, such as calcium carbonate, or sodium carbonate, and the like. In other preferred embodiments, the heat curable structural adhesive comprises silicate minerals, such as mica, as fillers.

In a preferred embodiment, the heat curable structural adhesive comprises at least one filler. In other preferred embodiments, the heat curable structural adhesive does not include a filler.

If the heat curable structural adhesive is foamable, it will contain one or more blowing agents (blowing agent) (blowing agents) that typically generate inert gases, which convert the adhesive into an open and/or closed cell structure (cellular structure). Expansion may help improve adhesion, sealing ability, acoustic damping, density reduction, or a combination of these factors.

The amount of blowing agent in the heat curable structural adhesive may vary widely depending on the desired type of cell structure, the desired amount of expansion of the heat curable structural adhesive, the melt viscosity of the ingredients, and the desired expansion rate.

Preferably, the heat curable structural adhesive comprises about 0.001 to 2 wt% of a foaming agent relative to the total weight of the heat curable structural adhesive.

The foaming agent may be a chemical foaming agent or a physical foaming agent.

Chemical blowing agents include, but are not limited to, compounds containing one or more nitrogen-containing groups, such as amides, amines, and the like. Examples of suitable chemical blowing agents include, but are not limited to, dinitroso pentamethylene tetramine, azodicarbonamide, dinitroso-pentamethylene tetramine, 4' -oxy-bis- (benzenesulfonyl hydrazide), trihydrazinotriazine, and N, N ' -dimethyl-N, N ' -dinitroso terephthalamide.

Physical blowing agents include, but are not limited to, solvent filled polymeric shells that soften and expand upon exposure to heat. Such physical blowing agents are commercially available, for example, akzo Nobel under the trade nameThe following products.

In a preferred embodiment, the heat curable structural adhesive comprises at least one blowing agent. In other preferred embodiments, the heat curable structural adhesive does not include a blowing agent.

A foaming promoter may be added to the heat curable structural adhesive in order to improve the properties of the foaming agent. The foaming promoter increases the rate at which the blowing agent forms inert gas.

Preferably, the heat curable structural adhesive comprises about 0.001 to 2 wt% of a foaming promoter relative to the total weight of the heat curable structural adhesive.

One preferred foaming promoter is a metal salt, such as an oxide, e.g., zinc oxide. Other preferred accelerators include, but are not limited to, organic bases such as urea, and organic acids such as adipic acid or benzoic acid. Zinc benzenesulfonate is also a suitable foaming promoter.

In a preferred embodiment, the heat curable structural adhesive comprises at least one foaming promoter. In other preferred embodiments, the heat curable structural adhesive does not include a foaming promoter.

In a preferred embodiment, the heat curable structural adhesive comprises a thermoplastic modifier or a mixture of various thermoplastic modifiers. This embodiment is particularly preferred when the heat curable structural adhesive contains neither a foaming agent nor a foaming promoter.

The thermoplastic modifier is typically a polyether that includes pendant hydroxyl moieties. The preferred thermoplastic polyether is a phenoxy resin.

For purposes of this specification, "phenoxy resin" refers to any polyhydroxy ether having phenyl ether linkages along the polymer backbone, and preferably also having pendant hydroxyl groups. Preferred phenoxy resins are derived from epoxides, preferably from bisphenol-A or bisphenol-F. However, these phenoxy resins have higher weight average molecular weights (typically in the range of about 25,000g/mol to about 100,000 g/mol) than the corresponding epoxy resins and are substantially free of epoxide groups (since terminal epoxy groups, if present, are negligible compared to the total size of the molecule).

Preferably, the heat curable structural adhesive comprises from about 3 wt% to about 40 wt%, more preferably from about 7 wt% to about 30 wt%, and most preferably from about 10 wt% to about 15 wt% of one or more thermoplastic modifiers relative to the total weight of the heat curable structural adhesive.

The preferred thermoplastic modifier is a phenoxy resin that is the reaction product of a phenolic difunctional epoxy resin and a difunctional phenol (e.g., the reaction product of epoxidized bisphenol a with bisphenol a). Similar materials can also be synthesized directly from bisphenols (e.g., bisphenol a) and epichlorohydrin. The terminal epoxy group may be ring opened to produce a terminal α -diol group.

In a preferred embodiment, the phenoxy resin is provided in the form of a phenoxy solution comprising a mixture of a first phenoxy resin comprising repeating units derived from bisphenol-a and a second phenoxy resin comprising repeating units derived from bisphenol-F. Preferably, the relative weight ratio of the first phenoxy resin to the second phenoxy resin is in the range of about 10:1 to about 1:2, more preferably about 5:1 to about 1:1, still more preferably 4:1 to about 2:1.

Other thermoplastic polyethers include, but are not limited to, aromatic ether/amine repeat units in their backbones, such as polyetheramines, poly (amino ethers), copolymers of monoethanolamine and diglycidyl ether, or combinations thereof, and the like. Examples of suitable thermoplastic polyethers are disclosed in U.S. Pat. No. 5,275,853, U.S. Pat. No. 5,464,924 and U.S. Pat. No. 3, 5,962,093.

Suitable phenoxy resins are commercially available under the trade name Inchem corpLower products (e.g., PKHH and PKHJ); products under the trade name Kukdo (e.g., YP-50); and CVC Thermoset Specialities under the trade name Epalloy (e.g., 8220).

In a preferred embodiment, the heat curable structural adhesive comprises at least one thermoplastic modifier, for example, a phenoxy resin. In other preferred embodiments, the heat curable structural adhesive does not include a thermoplastic modifier, e.g., no phenoxy resin.

In addition to the epoxy resin, curing agent, impact modifier, flexibilizer, blowing agent, filler, foam promoter, and/or thermoplastic modifier, the heat curable structural adhesive may also include one or more additional polymers, typically but not necessarily copolymers, and which include, but are not limited to, a wide variety of different polymers, such as thermoplastics, elastomers, thermosets, heat curable materials (thermosettables), combinations thereof, or the like.

When included in a heat curable structural adhesive, the primary purpose of these additional polymers is to provide more thermoplastic-like properties of the heat curable structural adhesive in the uncured state, including, for example, greater uncured flexibility, less tackiness in the uncured state, reduced cold flow prior to curing, improved processing when using typical polymer processing equipment. These additional polymers may also act as viscosity modifiers during the curing process to modify sagging and flow behavior.

For example, and without limitation, the heat curable structural adhesive may include one or more additional polymers independently selected from the group consisting of polyolefin, polyethylene, polypropylene, polyallylate, polyisobutylene, polyisoprene, polystyrene, polyacrylate (e.g., ethylene methyl acrylate copolymer), polymethacrylate, polymethyl methacrylate, polyacrylonitrile, polyacrylamide, polyacrylic acid, halogenated polymer, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyester, polyterephthalate, polyacetate, polyvinyl acetate (e.g., EVA), polycarbonate, polyketone polyether, polyethylene oxide, polyepoxide, polyurethane, polyamide, polyimide, polyethyleneimine, polysilane, silicone, polysiloxane, polysulfone, polyphenylene sulfide, polyphosphazene, polyphenolene (polyphenolics), rubber, polyphenylene oxide, or mixtures or copolymers thereof.

In a preferred embodiment, the heat curable structural adhesive comprises one or more ethylene polymers or copolymers, such as ethylene-acrylate copolymers, or ethylene-vinyl acetate copolymers, and the like. Ethylene-methacrylate copolymers and ethylene-vinyl acetate copolymers are particularly preferred ethylene copolymers.

Preferably, the heat curable structural adhesive comprises from about 0.1% to about 50% by weight, more preferably from about 1% to about 20% by weight, most preferably from about 5% to about 15% by weight of one or more additional polymers relative to the total weight of the heat curable structural adhesive.

In a preferred embodiment, the heat curable structural adhesive comprises at least one additional polymer. In other preferred embodiments, the heat curable structural adhesive does not include additional polymers.

The heat curable structural adhesive may include one or more polymeric or non-polymeric additives, agents or performance modifiers.

Such other additives, agents or performance modifiers include, but are not limited to, ultraviolet light blocking agents, flame retardants, heat stabilizers, colorants, processing aids, lubricants, slip agents, and adhesion promoters (tackifiers), among others.

Preferred adhesion promoters include, but are not limited to, amine or epoxy functional molecules, such as amine or epoxy functional silanes. An exemplary adhesion promoter is glycidoxypropyl trimethoxysilane, for example, commercially available from Dow Corning under the trade name Z-6040. Other tackifiers include, but are not limited to, aliphatic, aromatic, or aliphatic/aromatic petroleum resins, such as natural rosin ester tackifiers.

The heat curable structural adhesive may include a slip agent to facilitate processing. The viscosity required for processability depends on the processing technique and processing temperature to be employed. Examples of slip agents include, but are not limited to, oleamide and behenamide. However, slip agents reduce the Tg of the cured structural adhesive material, so their content (if any) should be minimized. Preferably, the amount of slip agent is no greater than 1% by weight relative to the total weight of the heat curable structural adhesive.

In a preferred embodiment, the heat curable structural adhesive comprises at least one such other additive. In other preferred embodiments, the heat curable structural adhesive does not include such other additives.

Another aspect of the invention relates to a method for producing a reinforcing member according to the invention as described above, said method comprising the steps of:

a. The carrier member is produced and the carrier member is,

B. cooling the carrier member, and

C. A heat-curable structural adhesive is produced which,

D. the carrier member is combined with the structural adhesive,

Wherein the material of the carrier member preferably comprises recycled polyester.

Preferably, the method of producing a reinforcing member according to the present invention as described above comprises the steps of: a. the carrier member is heat-processed by forming, preferably by compression forming, extrusion, pultrusion or injection molding,

B. cooling the carrier member, preferably cooling the carrier member or actively cooling it, and

C. The heat-curable structural adhesive is processed by forming the heat-curable structural adhesive on the carrier member (substrate), preferably by extrusion forming or preferably by overmoulding (overmoulding), i.e. injection moulding,

According to a preferred embodiment, the cooling in step b. Takes place in ambient air, irrespective of its relative humidity.

In step c, the heat curable structural adhesive may be applied to the carrier member by conventional methods such as melt coating, dipping, extrusion coating, and the like.

It may be important that during processing, the temperature is kept below the activation temperature that will cause the heat curable structural adhesive to cure (crosslink, harden) and foam (if a blowing agent is present).

The heat-curable structural adhesive is applied as a melt to the carrier member preferably at a temperature below the temperature at which curing and foaming occurs. The heat curable structural adhesive may be pelletized for extrusion and injection molding as a preferred method of application. After application, the resulting reinforcement member may be cooled to provide a dry feel to the heat curable adhesive layer on the carrier member. Optionally after transport, the carrier member may then be assembled with other components to be joined, and the heat curable structural adhesive then activated by heat, thereby exhibiting adhesive properties and forming a bond.

The invention also relates to a reinforcing member obtainable by the method according to the invention.

The activation of the heat curable structural adhesive may include at least some degree of foaming or frothing (foaming) in the case where the heat curable structural adhesive includes a foaming agent. Such foaming or foaming may help the heat curable structural adhesive wet the substrate and form a tight bond with the substrate.

The heat curable structural adhesive may be applied and activated in different ways and at different times depending on the intended application. Thus, exemplary uses of the reinforcing member according to the present invention are discussed below, illustrating preferred methods of application and activation. In particular, the reinforcing member may be used to reinforce, seal and bond, or to insulate panels (acoustic baffling) or the like, among others. Examples of potential uses are disclosed in US 7,125,461, US 7,892,396, WO 03/022953, EP 2 231 348 and GB 1201943.6.

As another example, the reinforcing member may be pressurized between the surfaces to be bonded together, and then the heat curable structural adhesive may be activated. It should also be appreciated that the surfaces to be bonded may be part of a single component or member, or part of two or more components or members that are bonded to each other by a heat curable structural adhesive, optionally additional bonding (attachment).

In one embodiment, the surfaces to be bonded are part of an automotive component. In such embodiments, the heat curable structural adhesive is typically activated at an elevated temperature employed in automotive paint drying operations (e.g., at a temperature common to e-coat or automotive paint operations, typically 120 ℃ to 250 ℃). Examples of structural adhesive applications are disclosed, for example, in US 6,887,914 and US 2003/0186049.

A further requirement of structural adhesives in certain applications, particularly in the automotive industry, is that they will bond to metal surfaces with stamping oil. Additionally, it is preferred that the heat curable structural adhesive will flow over the entire metal surface and bond to the metal surface more strongly than internal bonds within the structural adhesive (e.g., cohesive failure on the metal). This is assessed by separating the bonded metal surfaces and determining the percentage of surface area with adhesive.

Typically, the reinforcement member is applied as a preformed part. The reinforcing member may be shaped, for example by shaping or by extrusion and/or cutting, to form an article of substantially predetermined dimensions.

Thus, a further aspect of the invention relates to the use of a reinforcement member according to the invention as described above for bonding components of an automobile or an aircraft.

Another aspect of the invention relates to a method of bonding components of an automobile comprising the step of heating a reinforcing member as described above. Preferably, the heating is effected during an automotive electronic painting (e-coat) or paint spraying operation.

Another aspect of the invention relates to an adhesive assembly for an automobile or aircraft comprising a reinforcing member as described above.

Examples

The following examples and illustrations do not limit the scope of the invention. These explanations apply equally to all embodiments of the invention.

Two different reinforcement members are designed to form a part for the D-ring of the vehicle. The D-ring includes a D-ring and a cross beam (cross beam) of the vehicle. The reinforcement member is embedded in the structure of the vehicle to improve torsional rigidity (torsion stiffness) of the vehicle. The reinforcement member includes a carrier member.

According to comparative configuration 1, the carrier member is based on a fiber reinforced polyamide (PA 6GF 30). According to the invention, form 2, the carrier component is based on a fiber-reinforced polyester (PBT/PETGF).

The results are shown in the table herein below:

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Claims

1. A reinforcement member, comprising:

A foamable, heat-curable structural adhesive on an outer surface of a carrier member, the foamable, heat-curable structural adhesive foaming to no more than about 400% of its original unexpanded volume, wherein the carrier member has a cross-section that does not include a constant thickness throughout its elongation;

Wherein at least 90 wt% of the carrier member is composed of a fiber reinforced polyester material having a crystallinity of at least 60% and a content of fibers in the range of about 20-70 wt% relative to the total weight of the fiber reinforced polyester material;

And

Wherein the foamable heat curable structural adhesive forms a non-uniform coating along the thickness of the carrier member of 0.1mm to 3mm such that the exterior shape of the reinforcing member is different from the exterior shape of the carrier member, whereby the foamable heat curable structural adhesive forms a seamless connection with the carrier member.

2. The reinforcement member according to claim 1, wherein the foamable heat curable structural adhesive is post-formed to the carrier member after forming the carrier member.

3. The reinforcement member according to claim 2, wherein the reinforcement member has a hollow structure.

4. A reinforcing member according to claim 3 wherein the fibres are joined in bundles and the average length of the fibres is in the range of about 100 ± 50 μm.

5. The reinforcement member according to claim 4, wherein the foamable heat curable structural adhesive foams to no more than about 300% of its original unexpanded volume.

6. The reinforcement member according to claim 5, wherein the foamable heat curable structural adhesive foams to no more than about 200% of its original unexpanded volume.

7. The reinforcement member according to claim 6, wherein the content of the fibers in the fiber-reinforced polyester material is in the range of about 40-50 wt% relative to the total weight of the fiber-reinforced polyester material.

8. The reinforcement member according to claim 7, wherein the carrier member has an E-modulus of at least about 15GPa, the E-modulus being unaffected by the relative humidity of ambient air.

9. The reinforcement member according to claim 1, wherein the fiber-reinforced polyester material comprises a first polyester and a second polyester.

10. The reinforcement member according to claim 9, wherein the fibers are elongated carbon fibers.

11. The reinforcement member according to claim 10, wherein the first polyester is polybutylene terephthalate (PBT).

12. The reinforcement member according to claim 11, wherein the second polyester is polyethylene terephthalate (PET).

13. The reinforcement member according to claim 1, wherein the foamable heat curable structural adhesive is a coating of the fiber reinforced polyester material.

14. The reinforcement member according to claim 13, wherein the foamable heat curable structural adhesive covers at least about 50% of the outer surface of the carrier member.

15. The reinforcement member according to claim 9, wherein the relative weight ratio of the first polyester to the second polyester is in the range of about 1:10 to about 10:1.

16. The reinforcement member according to claim 15, wherein the first polyester, the second polyester, or both comprise recycled polyester.

17. The reinforcement member according to claim 10, wherein the fibers are substantially uniaxial particles.

18. The reinforcement member according to claim 9, wherein the fibers are glass fibers.

19. The reinforcement member according to claim 8, wherein the E-modulus is not moisture sensitive.

20. The reinforcement member according to claim 1, wherein at least 99 wt.% of the carrier member is comprised of the fiber-reinforced polyester material.